1. Field of the Invention
The present invention relates to the field of flat panel displaying, and in particular to a backlight module and a liquid crystal display device using the backlight module.
2. the Related Arts
Liquid crystal displays (LCDs) have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications, such as mobile phones, personal digital assistants (PDAs), digital cameras, computer monitors, and notebook computer screens.
Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise an enclosure, a liquid crystal panel arranged in the enclosure, and a backlight module mounted in the enclosure. The structure of a conventional liquid crystal panel is composed of a color filter (CF) substrate, a thin-film transistor (TFT) array substrate, and a liquid crystal layer arranged between the two substrates and the principle of operation is that a driving voltage is applied to the two glass substrates to control rotation of the liquid crystal molecules of the liquid crystal layer in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided from the backlight module in order to normally display images. Thus, the backlight module is one of the key components of the liquid crystal displays. The backlight modules can be classified in two types, namely a side-edge backlight module and a direct backlight module, according to the site where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the backside of the liquid crystal panel to form a planar light source directly supplied to the liquid crystal display panel. The side-edge backlight module comprises an LED light bar, serving as a backlight source, which is arranged at an edge of a backplane to be located rearward of one side of the liquid crystal display panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face at one side of the light guide plate and is projected out of a light emergence face of the light guide plate, after being reflected and diffused, to pass through an optic film assembly so as to form a planar light source for the liquid crystal display panel.
Referring to FIG. 1, a schematic view is given to illustrate a conventional liquid crystal display device, which comprises a backlight module 100, a mold frame 300 arranged on the backlight module 100, a liquid crystal display panel 500 arranged on the mold frame 300, and a bezel 700 arranged on the liquid crystal display panel 500. The backlight module 100 comprises: a backplane 101, a light guide plate 103 arranged in the backplane 101, a backlight source 105 arranged in the light guide plate 103. The backlight source 105 comprises a printed circuit board (PCB) 151 and a light-emitting diode (LED) chip 153 directly mounted on the PCB 151. The PCB 151 is arranged on a bottom plate 111 of the backplane 101 and the LED chip 153, which is set to correspond to a light incidence surface 131 of the light guide plate 103, is arranged between a side plate 113 of the backplane 101 and the light incidence surface 131 of the light guide plate 103. Compared to a conventional backlight module that comprises a backlight source arranged on a side plate, the backlight module 100 provides a reduced spacing distance between the light guide plate 103 and the side plate 113 of the backplane 101, making it advantageous in achieving bezel slimming of the liquid crystal display device. Further, to enhance heat dissipation performance of the backlight module 100, a heat dissipation board 107 is arranged between the PCB 151 and the bottom plate 111 of the backplane 101 to better transfer the heat emitting from the LED chip 153 to the backplane 101 to subject to heat exchange between the backplane 101 and the surroundings to dissipate the heat. This, although improving the heat dissipation performance, increases the thickness of the backlight module 100, thereby increasing the thickness of the entirety of the liquid crystal display device, this being opposite to the current trend of device thinning.